The present invention relates to an electrophoretic display device, to a method of manufacturing an electrophoretic display device and to an electronic apparatus.
With a rapid development in mobile data apparatus in recent years, increased demands have been made on power-thrifty and thin display devices. To meet these demands, various attempts have been made on development of techniques. Liquid crystal displays hitherto have met the demands.
However, in these liquid crystal displays, letters or characters become hard to read at some viewing angles to see a screen or due to reflected light, and light sources flicker. These problems place a burden on the visual sense and have not sufficiently been solved. Accordingly, researches on display devices that place a reduced burden on the visual sense have been made.
Reflective display devices are expected as a possible candidate for such display devices that consume reduced power and place a reduced burden on eyes. An electrophoretic display device (U.S. Pat. No. 3,612,758) is known as one of these reflective display devices.
FIG. 2 shows the principle of operation of the electrophoretic display device. This display comprises a dispersion liquid, a pair of transparent electrodes 14 and substrate 15 facing each other and sandwiching the dispersion liquid. The dispersion liquid comprises charged particles 11 and a colored insulating liquid 12. The charged particles 11 are particles bearing electrical charges, and the colored insulating liquid 12 contains a colored pigment dissolved therein.
The charged particles serving as electrophoretic particles bearing electrical charges are attracted to an electrode having an opposite polarity by applying a voltage through the electrodes. A display is produced by contrast between the color of the charged particles (electrophoretic particles) and the color of the colored insulating liquid. A desired display can be produced by forming one of the electrodes into a desired shape.
Specifically, when a voltage with some polarity is applied, for example, white charged particles (electrophoretic particles) are attracted to an electrode that is closer to a viewer, and a white display in a desired shape is produced against a background with the color of the colored insulating liquid. In contrast, when a voltage with the opposite polarity is applied, the charged particles are attracted to the opposite electrode, thereby allowing the viewer to recognize the color of the colored insulating liquid.
The electrophoretic display device was prepared by a process in which two plies of substrates 15, each carrying an electrode, were bonded together with the interposition of spacers 13, and thereby cells were formed. The resulting cells were filled with the dispersion liquid by making use of a capillary phenomenon.
However, such a conventional electrophoretic display device can only produce a binary display, i.e., a display by contrast between one pair of colors of a colored liquid and of charged particles, since a multiplicity of dispersion liquids with a multiplicity of colors cannot be disposed adjacent to each other. As a possible solution to this disadvantage, a process has been proposed in which several types of colored solutions (inks) containing dispersed charged particles are respectively discharged by an ink jet process. However, according to this process, the dispersion liquid contains the charged particles dispersed therein, and the discharged particles are liable to settle and cause clogging of nozzles.
The present invention has been accomplished to solve the above problems and to provide a method of manufacturing an electrophoretic display device that produces a display in multiple colors.
Specifically, a method of manufacturing an electrophoretic display device in accordance with the present invention comprises a pair of substrates and a rib that partitions a space into a plurality of cells, each filled with a liquid containing charged particles. The method comprises the steps of applying a liquid included in common by all the cells by using an application device, and allowing a discharge device to separately discharge a plurality of liquids so that the liquids differ in composition with respect to each of the plurality of cells and thereby fill in respective cells.
In the method of manufacturing an electrophoretic display device, the liquid included in common by all the cells is preferably a dispersive liquid. The dispersive liquid is preferably a liquid containing charged particles dispersed therein. Additionally, the discharged particles are preferably white particles and are preferably titanium dioxide particles.
The liquid included in common by all the cells is preferably a mixed solution containing a low boiling point solution and a high boiling point solution.
In the method of manufacturing an electrophoretic display device, the liquids that differ in composition with respect to each of the plurality of cells are preferably liquids each containing a dye dissolved therein.
In the method of manufacturing an electrophoretic display device, one of the pair of substrates is preferably a TFT substrate comprising a thin-film transistor formed thereon.
In the method of manufacturing an electrophoretic display device, the rib preferably comprises a material having rubber-like elasticity. The rib preferably comprises a material repellent to the liquid included in common by all the cells.
In the method of manufacturing an electrophoretic display device, the discharge device is preferably an ink jet device.
To solve the above problems, an electrophoretic display device of the present invention is manufactured by any of the methods of manufacturing an electrophoretic display device as described above.
An electronic apparatus of the present invention comprises the electrophoretic display device.